The present invention relates to dermatologically acceptable highly substantive oil-in-water emulsions. More specifically the present invention relates to an improved oil-in-water sunscreen composition. In a preferred embodiment, the sunscreen may be dispensed by a spray means.
There has been a long recognized need for a vehicle which is highly substantive, i.e. highly resistant to removal by water. Such a vehicle would be of particular interest in a sunscreen composition for use by bathers or any other persons whose occupation or life-style make it necessary to be exposed to the actinic rays of the sun.
In many countries, sunscreen formulations comprising oil-in-water emulsions, in which the feel is influenced by the aqueous phase during application, are preferred to water-in-oil emulsions, which have the feel of the oil phase.
Many of the sunscreen compositions which have been known heretofore have been relatively viscous and must be poured from the container into the hands for manual application to the body. In some commercial formulations having reduced viscosity, phase separation has occurred. Emulsions which have had relatively low viscosities frequently are not stable and have tended to separate into an oil phase and a water phase.
Accordingly, it would be desirable to provide an improved substantive oil-in-water emulsion having acceptable emulsion stability and adherence to the body so that it will not be easily removed by contact with water. The product should also exhibit cosmetic elegancy.
Australian Patent Publication No. 695,027 discloses the use of a water-in-oil emulsion comprising at least one oxyethylenated and oxypropylenated polyalkylpolyethersiloxane and at least one polymer exhibiting water-in-oil emulsifying properties. The emulsifier preferably is a polyhydroxylated block polymer with a polyethylene glycerol having 30 ethylene oxide units being particularly preferred.
We have found that a substantive agent comprising a block polymer containing poly(hydroxylated ester) blocks and polyethylene glycol blocks, such as PEG 30 dipolyhydroxystearate, has surprising utility in oil-in-water emulsions, particularly sunscreen compositions. We also surprisingly have found that the combination of this substantive agent with sunscreens permits the formulation of an improved oil-in-water sunscreen formulation having improved stability, low viscosity and cosmetic elegancy.